As it happens, I've just had a new inline thermostat fitted to one of my cars - until now, the temp gauge had never moved more than a couple of degrees above the quarter mark since I got it back in late August. I'll give you a rough guide of how mine goes, in case it's useful as a comparison. It's a 2001 CDT (to which Marinabrian gave the once-over before I brought it home
) and has a FBH.
Today was the first chance I had to look at the exact temperature figures, on a ten mile run to Ballycastle and then the return trip later. On the way out it started off at around 40 degrees, then over the course of about 4 or 5 miles it got up to above 80. The last couple of miles on the outward trip involved stop-start driving combined with bends etc, necessitating slower driving and so the temperature didn't rise above 83.
The trip home was an hour later, so with some residual heat in the engine it got up to above 80 degrees much more quickly, within maybe a couple of miles. The highest temperature displayed was when it flickered up to 87 degrees a couple of times, but generally it varied between 82 and 86. Interestingly, when I floored it on a couple of uphill stretches (to see whether that would make it rise to/above 90) it actually dropped fairly quickly from maybe 84/85 to 81. Dunno whether that was because of a sudden inrush of cold air maybe?
The ambient temperature was 7 degrees. I kept to anywhere between 15-30 mph in restricted areas and up to maybe 70mph when overtaking once. Most of the time the cabin temperature was sitting at 22 on the driver's side and 21 on the passenger side. The car has just had a full service including a full engine flush, oil change and new oil/air/fuel/PCV filters. The (non-bypassed) EGR valve & manifold have just been cleaned, but I haven't yet put in a dose of injector cleaner - the bottle is sitting in the car waiting till the next time I fill up.
Within a day or two I might be doing a slightly longer trip, so if that happens I'll let you know if I see anything different once I'm able to cruise at motorway speeds for a bit. Not expecting to do any trip over 20 miles each way till next week though. Let me know if there's anything to which you'd like me to pay particular attention.